The signaling pathways contributing to the polarized cytoskeleton of migrating neurons are not well understood. It is generally accepted that guidance cues play critical roles in establishing migration routes and axonal trajectories, but understanding how these factors signal to changes in the neuronal cytoskeleton remains an important topic. In my preliminary data, I have adopted an in vitro migration assay using primary neurons to model responses to these cellular cues, where cells undergo acute repolarization in response to a chemorepellent. I identified four stages that constitute this repolarization event. This research proposes to identify the roles of likely key regulators of these events: Rho-family GTPases Cdc42, Rac1, and RhoA, their effector protein IQGAP1, and +TIP microtubule (MT) tracking proteins EB1, CLIP-170 and APC. The spatio- temporal regulation and requirement of these molecules will be investigated using live-cell microscopy, fluorescently-tagged proteins, and genetic manipulation of gene expression and protein activity. These studies will provide mechanistic insight into cell polarity in migration, adding understanding to disorders that result from defects in neuronal migration including epilepsy, lissencephaly, and mental retardation. [unreadable] [unreadable]